This invention relates to a hinged device for forming a quadrilateral frame with a leg at each of its four corners. More particularly, the hinged device is especially useful for the quick assembly of a four-sided tubular frame within an excavation so that sheeting placed vertically against the outer edges of the frame will provide a protective enclosure against cave-in of the excavation.
Usually, excavators will improvise protection against cave-in by driving planks and sheeting into the soil at the bottom of the excavation and providing bracing members between planks positioned along opposite sides of the excavation. Such improvization requires much labor and time.
Many proposals have been made for the erection of protective shields within excavations. For example, recent U.S. Pat. No. 5,080,533 to Cooper shows a safety shield for an excavation consisting of vertical columns with horizontal steps to support horizontal sidewall members. Additionally, transverse bracing members are placed between the columns positioned along opposed sides of the excavation. U.S. Pat. No. 3,393,521 to Cammisa discloses a shoring frame having a basic component in the form of a vertical T-beam with T-sections welded to the opposite ends of the T-beam. Transverse braces have hooked plates on their ends to engage the T-sections. This hardware requires longitudinal timbers to complete the shoring frame. Both patents illustrate the failure of prior proposals to use a single, simple module that is readily interlocked with several such modules to form a shoring frame.
In spite of the diversity of structures that have been proposed to prevent cave-ins of excavations, none appears to have been simple enough to gain widespread use.
It is therefore a principal object of this invention to provide a simple module that can easily and quickly be used to assemble a quadrilateral tubular frame to support sheeting placed thereagainst.
Another important object is to provide such a module that is formed by merely a pair of hinged bars.
These and other features and advantages of the invention will be apparent from the description which follows.